They would all be viruses, since we can cure most bacterial infections if detected and treated early enough. They would also have to all be viruses without a good vaccine, since even an "incurable" virus can't harm you if you are immunized to it.
I would probably say: AIDS, influenza, hepatitis B for the top three. I don't know past that.
A virus like ebola has no known cure and something like a 90% mortality rate, but it is not that deadly in an epidemiological sense because it kills it's host so quickly. The most deadly viruses are ones like AIDS and influenza which leave the host alive for a long time so they can infect many more people.